Use a regex - you can select based on alternatives and also on digits. For example:
Would match 19/12/2012 and 01/06/1996 etc.
I'm not exactly sure what you are trying to do without sample input and outputs, but a regex is probably the way to go if you need to do complex text comparisons - that is exactly what they were developed for.
Get a copy of Expresso
] - it's free, and it examines and generates Regular expressions.